Questing

I am not a “lister.” Oh, I make lists; I’m just too absent minded to keep them. I do, however, go on quests. I have grail plants, grail critters, and even grail fungi. In a few cases, the quest is based on stunning appearance. For years, I planned journeys to go to wild and remote places to see Pileated Woodpeckers. Then I moved to Pennsylvania…where they feed regularly in the maple tree in my backyard. A bit of a let down, actually.

Pileated Woodpecker

But this Note is not about woodpeckers.

When it comes to grail critters, I am more often drawn by some aspect of behavior than to mere appearances. I want to see a Spitting Spider spit, some day. I want to see the mating dance of the Whooping Crane, some day.

And some day, I want to see North America’s only carnivorous butterfly1 caterpillar in action.

I know a site where there are aphids, and I have seen at least one adult at that site.

The adults don’t exactly catch the eye. They are small and yellowish, moth-like in their flight, and given to sitting very still for very long periods of time.

Harvester (flash photo)

I’ve never been close to one with its wings open, but I have spent considerable time dangling over three feet of water trying to focus and hold a camera steady to photograph one with its wings closed. The underwings are beautiful, a rich cinnamon rust with fine etchings. A note for photographers, they love to perch in the shadows, which will not give you accurate color; neither will flash—good luck: I did the best I could.

Harvester (no flash)

The very first two Harvesters I saw where absolutely besotted with the remains of a gutpile left by some considerate Nimrod in a nearby parking lot.4 They seemed to be sucking nutrients out of the adipocere5 that remained on the surface. This taste for things dead could be handy for locating colonies. Find the alders, find the aphids, throw a dead critter under the alders (get the land-owner’s permission), and check back frequently. I intend to try this next year.6

Harvester feeding on adipocere

Where there are adults, there should, eventually, be caterpillars. By all reports, they are very well camouflaged, even incorporating the aphids’ wool. Early observations led to the idea that the caterpillars spun webs to hide from the ants that usually attend the aphid colonies, but that theory has been called into question. More recent research indicates that the caterpillars are actually more likely to spin concealing webs when there are no ants. The ants are not the primary threat to the caterpillars. In fact, the ants, by protecting the aphids from other predators, also protect the caterpillars.7 The caterpillars fool the ants by incorporating chemicals from the aphids into their skin, which camouflages their scent.8

And the Harvester sings:

Larvae of F. tarquinius produced a call that, depending on the distance from the phonograph cartridge, resembled a mournful sigh, a falling glissando of six half-steps from F to middle C, or, at proximity, when amplified, the bleating of a sheep.9

Singing caterpillars: amazing, but not unique. In fact, Harvesters are part of a larger order called the Lycaenids, several of which depend on ants to complete their life cycles. The usual approach is to lure the ants into carrying the immature Lycaenid back to their nests, where the caterpillars feed in safety on food stored by the ants. Chemicals and calling are used to facilitate this deception.10

Wolf caterpillars in aphids’ clothing, even bleating like sheep; yep, I want to see that.

I have yet to find one. You have to go at exactly the right moment. They grow quickly. Most butterfly caterpillars have five stages (instars), the Harvester only has four. The entire period from hatching to pupating can take as little as eight days. I spent several hours searching the aphid colonies last summer, but I missed them.

There seems to be some debate over whether they winter as caterpillars or pupae, which I take to mean they probably will do either, depending on local conditions. So that is why I went wading in the little pond during last week’s warm spell. No, I was not expecting to find an errant larva in November, but I thought I might locate a pupa. No joy there either.

So the quest continues.

One of the most intriguing elements of a quest is serendipity. You often discover something marvelous that you did not set out to find. I’m sure this points to some great philosophical truth. I will have to think on it. Watch this space.

A little follow up: I got a very nice note informing me that there are, in fact, a couple of carnivorous moths in the genus Laetilia whose larvae eat scale insects. The Harvester is our only carnivorous butterfly caterpillar. [↩]

Feniseca is Latin for “one who mows.” The tarquinius refers to Tarquin the Great (or the cruel), last Etruscan king of Rome. Apparently the eminent early lepidopterist, Samuel H. Scudder, proposed a Feniseca porsenna—which would have been named after Lars Porsenna, king of Clusium, and an ally of Tarquin when they tried to re-take Rome. The Romans had run Tarquin off after his son, Sextus, committed the “deed of shame” against Lucretia (cf Shakespeare). All of this shows up in Macaulay’s splendid “Lays of Ancient Rome”; see, particularly, “Horatius” at the bridge. And as long as we’re wandering down this path, if you haven’t read Scudder’s essay on studying Grunts (a fish) for the famous Professor Agassiz, I highly recommend it. But I digress. [↩]

Note that, while the Harvester is North America’s only carnivorous butterfly caterpillar, it is not the only carnivorous caterpillar in the United States. When I lived in Hawai’i, I learned of a moth whose caterpillar was carnivorous. On researching this article, I learned that there are actually four Hawai’ian native moths in the genus Eupethecia that are carnivorous—and I came across this amazingYouTube™ video; enjoy. [↩]

Nimrod was a mighty hunter (Genesis 10; Chronicles 1). It is also the name of a splendid piece of music by Elgar. Most deer hunters leave the entrails deep in the woods. In this case, they were tossed under a bush next to the parking lot. I may be the only person in the county who considers that a good thing. Those little round things are poop. Olaus Murie intimated that one could discern the sex of the deer by the shape of the fecal pellets: round for does, bean-shaped for bucks. This has been disputed and is currently not considered valid. [↩]

For all those who don’t watch the forensic thrillers on TV, adipocere is the nasty yellowish waxy stuff that remains after the fat in the body breaks down. [↩]

Second note to photographers, they tend to return to the same perch over and over—just wait. [↩]

E. Youngsteadt and P. J. Devries, “The Effects of Ants on the Entomophagous Butterfly Caterpillar Feniseca tarquinius, and the Putative Role of Chemical Camouflage in the Feniseca—Ant Ineraction,” Journal of Chemical Ecology, 31, no.9, (September 2005). Available online at http://www.urbanwildlands.org/devries/YoungsteadtDeVries2005.pdf [accessed 1 December 2011]. [↩]

Ibid. The term camouflage is actually correct. “Chemical similarity is deemed mimicry if a parasite synthesizes host-like hydrocarbons or camouflage if the parasite incorporates host-synthesized hydrocarbons into its own cuticle.” Youngsteadt and Devries findings indicate that the caterpillars pick up the appropriate lipids from their prey. [↩]

This interaction between ants and other insects is called myrmecophily (literally, ant love—which, I must say, has a distasteful ring to it). The Lycaenids include the Blues and Hairstreaks; the Edward’s Hairstreak (Satyrium edwardsii) is myrmecophilous. That said, what the Harvesters do could scarcely be called love. [↩]

Cindy, thanks. I got some good feedback on the Harvester piece. It looks like I literally have to sneak up on the caterpillars. Apparently, if you jar the stem, they drop off on the ground. I didn’t know that.